Pinched-gap magnetic recording thin film head

ABSTRACT

An inductive pinched-gap thin film head (TFH) device having pole-tips which are in substantial contact in two areas, thereby precisely defining a pinched-gap segment. The substantial contact between the pole-tips effectively eliminates all flux lines emanating from the edges and corners during the write operation. The write magnetic field is thus precisely confined to across the pinched-gap segment. As a result, the written medium track width is accurately defined by the width of the pinched-gap segment with high degree of magnetization coherency and virtual elimination of the track-edge noise. The improved (medium) signal-to-noise ratio facilitates substantial increase of the track density. Photolithographic definition and etching of the gap-vias to the bottom pole-tip, followed by deposition of the top pole-tip, facilitates precise and consistent control of the width of the pinched-gap segment (and the written track) down to &lt;1 μm. The inductive TFH device may be fabricated in tandem with a magnetoresistive (MR) read device, with one of the pole-tips of the inductive TFH device being substantially wider than the other pole-tip and serving also as a magnetic shield for the read element in the MR device.

This application is a continuation-in-part of pending application Ser.No. 07/963,783, filed Oct. 20, 1992.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to magnetic thin film heads (TFH) for recordingand reading magnetic transitions on a moving magnetic medium.

2. Background of the Invention

Magnetic TFH transducers are known in the prior-art. See, e.g. U.S. Pat.Nos. 4,016,601; 4,190,872; 4,652,954; 4,791,719 for inductive devicesand U.S. Pat. Nos. 4,190,871 and 4,315,291 for magnetoresistive (MR)devices.

In the operation of a typical inductive TFH device, a moving magneticstorage medium is placed near the exposed pole-tips of the TFHtransducer. During the read operation, the changing magnetic flux of themoving storage medium induces changing magnetic flux upon the pole-tipsand gap between them. The magnetic flux is carried through the pole-tipsand back-portion core around spiralling conductor coil winding turnslocated between the core arms. The changing magnetic flux induces anelectrical voltage across the conductor coil. The electrical voltage isrepresentative of the magnetic pattern stored on the moving magneticstorage medium. During the write operation, an electrical current iscaused to flow through the conductor coil. The current in the coilinduces a magnetic field across the gap between the pole-tips. A fringefield extends into the nearby moving magnetic storage medium, inducing(or writing) a magnetic domain (in the medium) in the same direction.Impressing current pulses of alternating polarity across the coil causesthe writing of magnetic domains of alternating polarity in the storagemedium. Magnetoresistive (MR) TFH devices can only operate in the readmode. The electrical resistance of an MR element varies with itsmagnetization orientation. Magnetic flux from the moving magneticstorage medium induces changes in this orientation. As a result, theresistance of the MR element to a sensing electric current changesaccordingly. The varying voltage signal is representative of themagnetic pattern stored on the magnetic medium.

Prior-art magnetic recording inductive thin film heads include top andbottom magnetic core pole layers, usually of the alloy Ni--Fe(permalloy), connected through a via in the back-portion area, andseparated by a thin gap layer between the pole-tips in the front of thedevice. The bottom pole-tip is usually designed to be wider than the toppole-tip in order to prevent "wraparound" due to misregistration ormisalignment, as taught by R. E. Jones in U.S. Pat. No. 4,219,855.Alternatively, one or both pole-tips are trimmed by ion-milling or byreactive ion etching (RIE) to ensure similar width and proper alignment.Such a technique is disclosed, for example, by U. Cohen et al. in U.S.Pat. No. 5,141,623. As the track width decreases in order to increasethe recording density, the write head pole-tips must be very narrow. P.K. Wang et al. describe elaborate schemes to obtain pole-tips forwriting very narrow track width, in IEEE Transactions on Magnetics, Vol.27, No. 6, pp. 4710-4712, November 1991.

One of the problems associated with the prior-art pole-tip designs isthat during write operations, substantial noise is introduced along thetrack-edges (on the magnetic storage medium), which adds to the noisegenerated by the medium during read operations. During the writeoperations, significant portions of the intense magnetic flux lines,emanating from the corners and side-edges of the pole-tips, deviate froma direction parallel to the track's length. The non-parallel magneticfield magnetizes the medium in the wrong directions, giving rise tonoise along the track-edges. This noise is usually characterized as"track-edge fringing noise" and is a major obstacle to increasing thetrack density. According to a paper by J. L. Su and K. Ju in IEEETransactions on Magnetics, Vol. 25, No. 5, pp 3384-3386, September 1989,the track-edge noise extends about 2.5 μm on each side of the writtentrack. In the commonly used conventional merged MR (MMR)( )design, thebottom pole-tip of the inductive write element is also used (or shared)as the top shield for the MR read element. In order to be an effectiveshield, it must be much wider than the top pole-tip. This furtheraggravates the track-edge fringing noise introduced by side-writing. Thehigh track-edge noise and wide erase (or write) width produced by theconventional MMR design, limits its usefulness to relatively low trackdensities. As track density increases, the track width decreases alongwith the strength of the read-back signal. If the track-edge fringingnoise remains the same, then the signal to noise ratio (SNR) is directlyproportional to the track width, and deteriorates rapidly as the latterdecreases. The current state-of-the-art magnetic thin film media cansupport lineal density of about 40,000-60,000 flux changes per inch(FCI), corresponding to domain length of about 0.4-0.7 μm. Yet, thetrack width is at least an order of magnitude larger, about 8-12 μm.There is no apparent reason why the media could not support muchnarrower tracks, if not for the rapid deterioration of the SNR. Byeliminating most of the track-edge fringing noise, the useful trackwidth could be decreased to about 1.0 μm, or less. This represents anincrease of recording density by about an order of magnitude.

In addition to the medium's noise, there is also the head's noise. Asignificant portion of the head's noise is due to edge-closure domainsin the pole-tips. This noise contribution becomes more dominant as thewidth of the pole-tips decreases. This problem was described, forexample, by D. A. Herman in Paper No. 299, "Laminated Soft MagneticMaterials", The Electrochemical Society Conference, Hollywood, Fla.,October 1989.

SUMMARY OF THE INVENTION

The present invention provides an inductive "pinched-gap" thin film head(TFH) device having pole-tips that are in substantial contact in twoareas, thereby enclosing a pinched-gap segment between the areas ofsubstantial contact. The magnetic material in each area of substantialcontact is referred to as a "magnetic shunt". Since no magnetic fluxlines emanate from the corners and side-edges of the pole-tips, thewrite magnetic field is precisely confined to across the pinched-gapsegment in a direction parallel to the track's length. As a result, theusual noise-producing non-parallel magnetic field from the pole-tips'corners and side-edges is virtually eliminated. The written (medium)track width is precisely defined by the width of the pinched-gapsegment. It incorporates a high degree of magnetization coherency and issubstantially free of the track-edge noise.

An effective technique to confine the gap includes photolithographicdefinition and etching gap-vias through the gap to the bottom pole-tipsides or side-edges, followed by deposition of the top magnetic pole.The distance between the gap-vias defines the width of the pinched-gapsegment, which in turn accurately and consistently determines the widthof the written track. The total width of the pole-tips is not as crucialas in prior-art devices. Either one or both pole-tips may be depositedwider than their final dimension and, following the top pole deposition,trimmed by ion-milling or by reactive ion etching (RIE) to their finalwidth.

Alternatively, one pole-tip (usually the bottom) may be made wider thanthe other. In the case of the merged MR (MMR) TFH device, for example,the bottom magnetic pole-tip serves also as the top magnetic shield forthe MR read element. The latter must be much wider than the top pole-tipin order to be an effective shield for the MR element. It is notnecessary to trim the bottom magnetic pole following the deposition ofthe top magnetic pole and formation of the gap-pinching magnetic shunts.Similarly, a conventional (read/write) inductive TFH device may also befabricated with one of the pole-tips wider than the other pole-tip.Depositing wider pole-tips improves the composition and thicknessuniformities of the device.

Alternatively, intentional wraparound on both sides of the bottompole-tip also produces a confined gap segment with substantial contactof the pole-tips along their side-edges. Depositing a top pole-tip thatis wider than the bottom one readily produces such a wraparound. Thewidth of the pinched-gap segment (as well as the track width) isdetermined by the width of the bottom pole-tip. Incomplete step coverageby the gap layer at the side-edges of the bottom pole-tip providessubstantial contact there. To ensure contact along the upper corners ofthe bottom pole-tip, they can be exposed by ion-milling (with a thinmask) or by etching gap-vias prior to the deposition of the top pole.Excess width of the top pole-tip on both sides of the bottom pole-tipcan be trimmed by ion-milling, RIE, or by chemical etching.

Although the pinched-gap transducer's efficiency is not adverselyaffected in the write operation, it may be impaired in the read mode dueto the partial shorting of the pole-tips. A dual-element or tandem (oneon top of the other) TFH device, combining a pinched-gap TFH device as awrite element, and a separate TFH device as a read element may beadvantageous. The pinched-gap TFH device is particularly suitable foruse as a write element in combination with a separate read element, suchas a magnetoresistive (MR) element, or another inductive TFH elementoptimized for the read operation. Much of the head's noise, such asBarkhausen pop-corn noise, or glitch after write, is related to thewrite operations. In a dual-element device combining the pinched-gap asthe write element, such noise is irrelevant since it does not interferewith the read-back and verification operations. These functions areexecuted by the separate read element. Also, the pinched-gap TFH deviceexhibits less noise due to the elimination of the edge-closure domainsin the pole-tips. This is particularly true when the pinched-gap deviceis used in the write mode, but it is also effective in the read mode.Combining a pinched-gap write element with an MR read element isparticularly advantageous, especially for high density small form diskdrives. However, the fabrication of the additional MR element is highlycomplex and very costly. A simpler and more economic solution is tofabricate a separate inductive TFH element, optimized for the readoperation.

The read and write TFH elements can preferably be situated or placedside-by-side on the same rail (or air bearing surface) or on differentrails of the slider. Such a layout requires a fixed-translation of theslider to position the read element over the written track after a writeoperation. However, such a short translation takes only a very shorttime. Alternatively, multiple sliders per disk surface, attached toseparate actuators, can be positioned in such a way that the readelement of the second slider follows directly behind the track of thefirst slider's write element. Such a track-following scheme minimizesthe time lapse between a write and a read-back or verificationoperations. These fixed-translation and track-following schemes can alsoapply for a dual element or tandem combination of an inductive writeelement and an MR read element.

The pinched-gap TFH device of this invention may also be used withcontacting heads, such as in magnetic tape recording devices or contactrecording disk drives. Such heads may be positioned in sliders havingone or more sliding rails.

An object of this invention is to provide a pinched-gap TFH device forwriting media tracks virtually free of track-edge noise.

Another object is to provide a pinched-gap TFH device having accuratelyand consistently defined narrow pinched-gap segment and capable ofwriting narrow tracks, down to ≦1 μm.

An additional object is to decrease the head's noise by reducing theedge-closure domains along the side-edges of the pole-tips.

Another object of the invention is to provide methods for making thepinched-gap TFH device.

A still further object of this invention is to provide a dual-elementTFH device with a pinched-gap write element and an MR or inductive TFHread element.

Another object is to provide a pinched-gap TFH write element combined intandem with an MR read element.

An additional object is to provide a pinched-gap TFH write element aspart of a tandem merged MR (MMR) device.

An additional object is to provide a dual-element TFH device having theread and write elements placed side-by-side on the same rail (or airbearing) or on separate rails of the slider.

A further object of the invention is to provide a fixed-translationprocedure for a read-back or verification of a written track, using thedual-element TFH device with side-by-side elements on the same rail oron separate rails of the slider.

Another object is to provide a track-following scheme for multipleactuators having more than one head per disk surface, to minimize thetime lapse between the write and read-back or verification operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior-art wraparound top pole-tip, as seen from the airbearing surface (ABS).

FIG. 2 shows a prior-art configuration, with the bottom pole-tip beingwider than the top pole-tip.

FIG. 3 shows a prior-art ion-milled bottom pole-tip.

FIG. 3a shows a prior-art configuration of a tandem merged MR (MMR)device with the bottom pole-tip wider than the top pole-tip.

FIG. 4 is a schematic view of a prior-art written track with track-edgefringing noise.

FIG. 5 shows a pinched-gap and pole-tips, as seen from the ABS,according to a preferred embodiment of this invention.

FIG. 5a shows a pinched-gap write element combined with an MR element inan MMR configuration, according to a preferred embodiment of thisinvention.

FIG. 6 illustrates a technique for photolithographic definition andetching of gap-vias to confine a pinched-gap segment, according to apreferred embodiment of the invention.

FIG. 7 shows wraparound on both sides producing a confined gap segmentwith virtual shorting along the side-edges of the bottom pole-tip.

FIG. 8 illustrates thin ion-milling mask faceting, exposing the topcorners of the bottom pole-tip, to facilitate pinching of a gap segmentby wraparound.

FIG. 9 illustrates an alternative embodiment using photolithographicdefinition and etching of gap-vias combined with wraparound to confine apinched-gap segment.

FIG. 10 shows a schematic of a written track with no track-edge fringingnoise, obtained by using a pinched-gap TFH device.

FIG. 11 illustrates a dual-element pinched-gap write element placed ontop of an MR read element, as seen in perspective from the air bearingsurface (ABS).

FIG. 12 illustrates a side-by-side dual-element comprising a pinched-gapwrite element and an MR read element on the same rails, as seen inperspective from the ABS.

FIG. 13 illustrates a dual-element comprising a pinched-gap writeelement and an MR read element placed on separate rails, as seen inperspective from the ABS.

FIGS. 14a-14c illustrate a method of forming a pinched-gap structurewith a wide bottom pole-tip, such as required in MMR devices, as seenfrom the ABS.

FIGS. 15a-15d illustrate an alternative method of forming a pinched-gapstructure with a wide bottom pole-tip, such as required in MMR devices,as seen from the ABS.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an air-bearing surface (ABS) view of a frequently occurring"wraparound" situation due to misregistration or misalignment ofprior-art pole-tips of similar width. The head is usually formed upon anon-magnetic wafer substrate 10 comprising a ceramic compound such asAl₂ O₃ -TiC, and a non-magnetic, insulating undercoat 12 consistingusually of Al₂ O₃. The magnetic top pole-tip 18 wraps around one edge ofthe bottom magnetic pole-tip 14. The magnetic core poles consist of aferromagnetic material having a low coercivity and high saturation andpermeability, such as permalloy Ni--Fe. A non-magnetic gap layer 16,consisting usually of Al₂ O₃, separates pole-tips 14 and 18. Due toincomplete step coverage by gap layer 16 over the side-edges of bottompole-tip 14, the two pole-tips may contact or short (or virtually short)at the wraparound site. The wraparound situation is predominant when thetop pole-tip is wider than the bottom one.

U.S. Pat. No. 4,219,855 discloses a TFH device with pole-tips havingunequal widths, as shown in FIG. 2. The wider bottom pole-tip helps toprevent the wraparound situation. The difference in width between thetwo pole-tips is typically about 3-5 μm. Track-edge noise, introduced bynon-parallel (to the track's length) magnetic field emanating from thecorners and side-edges of the pole-tips during the write operation, isvery significant when the width of the pole-tips is unequal. Also, thewritten track width is ill-defined, and varies with the write currentand the alignment of the pole-tips. As track width decreases to allowfor higher track density, such a difference becomes unacceptable, andother schemes allowing for pole-tips having more equal widths becomemore prevalent. One or both pole-tips can be trimmed by ion-milling orby reactive ion etching (RIE) to ensure similar width and properalignment. An example of ion beam pole-trimming is disclosed in U.S.Pat. No. 5,141,623, as shown in FIG. 3. Although pole-trimmingsignificantly improves (or decreases) the feasible track width, there isstill substantial track-edge noise introduced by the non-parallel writemagnetic field emanating from the corners and side-edges of thepole-tips. The side-writing problem is particularly serious in theconventional merged MR (MMR) device shown in FIG. 3a. (In FIG. 3a, thesubstrate and the undercoat are omitted for simplicity.) Bottom pole-tip14 is also shared (or merged) as the top magnetic shield for the MR readdevice, which also includes an MR read element 17, a read-gap 15 and abottom magnetic shield 13. In order to be an effective shield, bottompole-tip/top magnetic shield 14 must be much wider than the top pole-tip18. As a result, side writing and erase width are large and sensitive tothe amplitude of the write current.

FIG. 4 shows schematically the resulting written track and associatedtrack-edge noise, obtained by using prior-art inductive TFH heads.

FIG. 5 shows a preferred embodiment according to this invention. Areasof substantial contact are established between the bottom pole-tip 14and top pole-tip 18, thereby "pinching" or confining a gap segment 16.The width of the pinched-gap segment, W, is the lateral distance betweenthe areas of the pole-tips that are in substantial contact, and thethickness of the pinched-gap segment, G, is the vertical distancebetween the pole-tips. In the preferred embodiment bottom pole-tip 14and top pole-tip 18 are in actual physical contact. However, this is notabsolutely necessary, and in other embodiments a small "gap" mayseparate the bottom and top pole-tips. This small "gap" or separationshould be small enough to prevent the magnetic flux lines from emanatingsignificantly from the pole-tips in those regions. The separation of thepole-tips in the areas of substantial contact should not exceed about25% of G, and preferably be less than 5% of G, the thickness of the gaplayer between the pole-tips across the pinched-gap segment. Preferablythe structure illustrated in FIG. 5 should extend all the way up thepole-tip to zero throat height, the point where the poles begin todiverge, and also where the back-portions (not shown) begin.

FIG. 5a illustrates another embodiment of the invention in which apinched-gap write element is combined in a merged MR (MMR) structure.Bottom pole-tip 14 of the write element is also used for (or shared) asthe top magnetic shield of the MR read element. MR element 17 andelectrical contacts and/or track-defining contacts 17a are locatedinside read-gap 15. Write-gap 16 is the pinched-gap segment confinedbetween magnetic shunts 19a and 19b, which provide substantial contactbetween top magnetic pole-tip 18 and bottom magnetic pole-tip/top shield14.

As used herein, the term "substantial contact" includes actual physicalcontact between the pole-type as well as a condition in which there is asmall gap between the pole-tips such that the magnetic reluctancebetween the pole-tips is substantially reduced and the magnetic fluxlines are therefore prevented from extending from the area ofsubstantial contact contact to a degree that significant track edgenoise is created.

While gap 16 in FIGS. 5 and 5a is formed of Al₂ O₃, it may alternativelybe formed of any non-magnetic material, including SiO₂, SiO or SiN_(x)and non-magnetic metals such as Cu, Al, Ag or Au. Pole-tips 14 and 18are preferably formed of Ni--Fe but may also be formed of otherferromagnetic materials such as ferrites, sandust (Fe--Ai--Si), Co--Fe,Co--Ni--Fe, Co--Zr, Co--Nb--Zr, Co--Ta--Zr, Co--Mo--Zr, Co--W--Zr,Fe--N, Fe--Al--N, Fe--Si--N, and laminated poles comprisingferromagnetic layers alternating with non-magnetic layers. Thegap-pinching magnetic shunts 19a and 19b of FIG. 5a may consist of thesame soft ferromagnetic material(s) used for forming the pole-tips 14and 18 or they may comprise other soft ferromagnetic material(s). Forsimplicity of fabrication, it is convenient to form shunts 19a and 19bof the same material used for the top pole-tip 18. However, otherferromagnetic materials may be more suitable for the shunts, in order tobetter match the shunt reluctance to that of the pinched-gap segment 16,for optimum performance of the device. Different ferromagnetic materialsmay be used to construct top and bottom pole-tips 14 and 18. Therelative reluctances are also determined by geometrical dimensions suchas the cross-sectional area of shunts 19a and 19b and their lengthversus the cross-sectional area and length (thickness) of thepinched-gap section 16. Reluctance is proportional to the length andinversely proportional to permeability and cross-sectional area. Atrelatively low shunt reluctance, a large fraction of the magnetic fluxwill be shunted, thus adversely affecting the obtainable magnitude ofthe write field across the pinched-gap segment 16. 0n the other hand, anexcessively high shunt reluctance may not be capable of effectivelyeliminating the side write field. An optimum balance or reluctancematching may be required for different pinched-gap segment and pole-tipgeometries. It should be noted that while the permeability of the gapmaterial is constant (μ=1) with the magnetic flux density (B), thepermeability of the soft ferromagnetic shunt material is very high atlow flux density (μ>1,000) and approaches unity as flux densityapproaches saturation. Thus if the total flux is low, most of the fluxwill be channeled through the shunts 19a and 19b. As the total fluxincreases (by increasing the write current and/or the number of coilturns), the reluctance of the shunts 19a and 19b will increase, forcinga larger fraction of the flux to be directed over the pinched-gapsegment 16 and thereby increasing the write field there.

In the pinched-gap TFH device, the length of the shunts 19a and 19b isequal to the length (or thickness) G of the pinched-gap segment 16. Thecross-sectional area of each shunt is determined by its width, (W_(P)-W)/2, multiplied by its depth. The shunt depth may extend over theentire throat height, from the front ends of the pole-tips to zerothroat (where the poles begin to diverge), or the depth may be shorter.In the latter case, the shunt depth extends from the front ends of thepole-tips to some positive throat height. Although it is more convenientto fabricate the gap-pinching shunts with the entire throat heightdepth, it may be advantageous to fabricate them with shorter depth.Shorter shunt depth increases their relative reluctance versus that ofthe pinched-gap segment. Similarly, decreasing the shunt width willincrease their relative reluctance. In order to ensure adequate writefield of the pinched-gap TFH device, sufficient flux must reach the poletips without saturation anywhere else in the device. In particular, itis important to maintain the pole-tips' thickness larger than the throatheight and, preferably, at least twice as large. Also, the back viaconnecting the top and bottom yokes should be wide enough to avoidsaturation.

To facilitate the closure of the pole-tips, vias can be defined byphotolithography and etched through the gap layer to delineate thecontact areas. After depositing the top magnetic pole, the pole-tipscontact each other through the gap-vias. Either one or both pole-tipscan then be trimmed by ion-milling or by RIE to define their finalwidth, W_(P). Using photolithographic definition of the gap-vias, it ispossible to accurately and consistently control the width of thepinched-gap segment, W, down to ≦1 μm. The gap-vias to the bottompole-tip can be defined and etched at the same time during the formationof the back-portion closure gap-vias, by using a proper mask, to saveprocessing steps. Otherwise, they can be done separately with separatemasks. Definition and etching of the gap-vias can be performed at anystage following the deposition of the gap layer. However, it ispreferable to postpone these operations until after the completion ofall the coil and insulation layers and studs (if used), until just priorto the deposition of the top magnetic pole. This prevents attack onand/or contamination of the vias and the exposed bottom pole areas bythe numerous processing steps.

FIG. 6 illustrates an effective technique for lithographic definition ofthe pinched-gap segment, according to a preferred embodiment of thisinvention. The figure shows the stage after a photoresist layer 22 hasbeen coated and patterned by exposing through an appropriate mask anddevelopment. W is the lateral distance between the inside-edges of thevias, and L is the distance between the outside-edges of the vias. Priorto coating the photoresist layer, a thin metallic layer 20 was depositedover gap layer 16. The purpose of metallic layer 20 is to provide animproved etch mask for the gap-vias. Although a photoresist mask aloneis compatible with a gap-etchant based on phosphoric acid (diluted withwater to a volume ratio of about 1:1, and operated at 60°-80° C.), theetching rate is rather slow and non-uniform. It is very sensitive to theaspect ratio of the mask features and to the flow pattern and rate ofthe etchant. Small opening features (with high aspect ratio) etch slowerthan larger ones. Also, once the gap is etched away this etchant beginsto attack the underlying permalloy bottom pole 14. In particular itattacks defective spots in the permalloy, creating deep craters in theexposed areas under the gap-vias. A preferable gap-etchant is based ondilute HF in water. It provides faster and much more uniform etching,since it is less sensitive to the aspect ratio and flow pattern or rate.However, photoresist mask 22 alone may not be sturdy enough when usingsuch an etchant. The latter attacks rapidly the interfacial bond betweenthe photoresist and the alumina gap layers, if no metallic layer isinterposed between them. The rapid lateral attack results in severeundercutting and occasional lift-off of the photoresist layer during thegap-etching operation.

Metallic layer 20 must have good adhesion to gap layer 16, and must besubstantially immune against attack or etching by the gap-etchant.Metallic layer 20 can be deposited by a vacuum technique, such assputtering or evaporation. It may comprise a metal selected from thegroup Ni--Fe, Cr, W, Ta, Mo, Nb, V, and alloys comprising one or more ofthese metals. It may also include metals with weaker adhesion to thegap, such as Cu, Au, Ag, Pd, Pt, Rh, Ir, or alloys comprising one ormore metals thereof, particularly if they are preceded by a metal layerwith stronger adhesion to the gap, such as Cr. The thickness of thislayer can be as low as 30-50 Å, and preferably be in the range 100-300Å. In the preferred embodiment, metallic layer 20 comprises a singlepermalloy (Ni--Fe) layer with thickness between 100-300 Å.

The pattern of the vias is next transferred to metallic layer 20 byetching with a selective etchant through photoresist mask 22. Thisetchant must be compatible with the photoresist mask, and should notsignificantly attack or etch gap layer 16. In the preferred embodiment,a selective etchant for the Ni--Fe layer 20 comprises nitric acid,phosphoric acid, and water in a volume ratio of 1:1:8, as described inU.S. Pat. No. 5,059,278, incorporated herein by reference.

Following the etch-transfer of the via pattern to metallic layer 20,gap-vias are etched through the reinforced mask (combining both metalliclayer 20 and photoresist 22). An adequate gap-etchant consists of diluteHF in water:

    ______________________________________                                        Hydrofluoric Acid (48%)                                                                          HF        1 volume                                         Water              H.sub.2 O 9 volumes                                        ______________________________________                                    

This corresponds to 10% concentration by volume (v/v), or to 4.8% byweight (wt %). The etchant is operated at room temperature with moderateagitation or spraying. The etch rate increases by raising thetemperature or the HF concentration. The operating temperature can be inthe range 10°-90° C., and preferably at room temperature, forconvenience. The etchant may comprise HF and water in concentrationrange 5-25% v/v of concentrated (48%) HF (2.4-12.0 wt. % of HF), andpreferably in the range 8-15% v/v of concentrated (48%) HF in water(3.8-7.2 wt. % of HF). Other chemicals, such as alcohols or ethyleneglycol, may also be added to or substituted for all or a portion of thewater.

Following the etching of the gap-vias, photoresist layer 22 is removedusing a conventional stripping method. Next, metallic layer 20 isremoved by a wet chemical etching or by a dry etching technique such assputter-etching or ion-milling. In the first case, it may be removed bythe same wet etchant which was previously used to pattern this layer. Ifthis etchant can also attack the bottom magnetic pole 14, then it may beadvantageous to use one of the dry etching techniques. In either case,keeping the thickness of layer 20 to a minimum ensures minimal attack onlayers 14 and/or 16 during the removal of metallic layer 20. In thepreferred embodiment, the Ni--Fe layer 20 is removed by a briefsputter-etching or ion-milling step. Alternatively, if metallic layer 20consists of permalloy, and the gap-vias are etched just prior to thedeposition of the top (permalloy) magnetic pole, then layer 20 can beleft in place to become a part of the magnetic pole. If layer 20consists of a different metal or alloy than the pole(s), then it ispreferentially removed by a selective wet chemical etchant which doesnot attack either layer 14 or 16. When the top magnetic pole isdeposited, it makes physical contacts to the bottom pole-tip through thegap-vias. A pinched (or confined) gap segment with a well-defined width,W, is thus constructed. The excess width of one or both pole-tips can betrimmed by ion-milling or by RIE to their final width, W_(p), to producethe structure of FIG. 5.

In another embodiment, bottom pole-tip 14 is originally patterned widerthan the top pole-tip 16, so that W₁ >W₂, where W₁ is the bottompole-tip's width and W₂ is the top width of the pole-tips width. Thelatter is equal to the final width of the pole-tips, W_(P), which is inthe range W<W₂ =W_(P) <L, as shown in FIG. 6. Following the top poledeposition, the excess width of the bottom pole-tip (over W_(P)) istrimmed by ion-milling or by RIE, in accordance with U.S. Pat. No.5,141,623, incorporated herein by reference. The lithographic etchingtechnique is highly precise and accurate and can consistently produce apinched-gap segment with a width W≦1 μm.

In another embodiment, wraparound on both sides of the bottom pole-tipproduces a confined or a pinched-gap segment with substantial contactalong the side-edges of the bottom pole-tip. Depositing a wider toppole-tip than the bottom one, readily produces such wraparound on bothsides, as shown in FIG. 7. Due to incomplete step coverage by the gaplayer around the side-edges of the bottom pole-tip, substantial contactis accomplished there after deposition of the top pole (see Example 2).Excess width of the top pole-tip can be trimmed by ion-milling or byRIE. To ensure consistent contacts along the side-edges and uppercorners of the bottom pole-tip, they can be exposed by a briefion-milling using a thin etch mask, as shown in FIG. 8. Due to faceting,the thin etch mask is consumed faster at its edges, exposing the gap atthe pole-tip's corners and side-edges to the ion-milling process.Alternatively, gap-vias can be lithographically defined and etched alongthe side-edges of the bottom pole-tip, as shown in FIG. 9. The width ofthe pinched-gap segment, W, is equal to the width of the bottompole-tip, W₁, in the cases of FIGS. 7 and 8, and to the lateral distancebetween the vias in the case of FIG. 9. Again, the excess width of thetop pole-tip on both sides of the bottom pole-tip can be trimmed to itsfinal width by ion-milling, RIE, or by chemical etching.

FIG. 10 shows schematically a (medium) track written with a pinched-gapinductive TFH head. The track boundaries are precisely defined and itswidth, W_(T), is substantially equal to the width of the pinched-gapsegment, W. It may be slightly wider (by a small fraction of onemicrometer), due to a diverging write field in the space between thepole-tips and the (medium) magnetic layer. The smaller this space, thesmaller is the difference between W and W_(T). For the state-of-the-artflying height, d<1,000 Å, the width of the written track W_(T) issubstantially the same as the width of the pinched-gap segment, W. Thisis in sharp contrast to tracks written by prior-art TFH devices (shownin FIG. 4), where W_(T) is wider than W by several micrometers. Thetrack-edge noise of the latter is created by the non-parallel writemagnetic field emanating from the corners and side-edges of theconventional TFH devices. The non-parallel magnetic field also widensthe track width, causing the track edges to be blurred and indefinite.

The shorted pole-tips do not adversely affect or reduce the desirablemagnetic field across the pinched-gap segment during a write operation,since it is a common practice to saturate the pole-tips during thisstage. The only emanating flux lines between the pole-tips are confinedto across the pinched-gap segment. The flux lines thus substantiallycomprise only the desirable direction parallel to the track's length.Although the pinched-gap transducer's efficiency is not adverselyaffected in the write mode, it may be impaired in the read mode. Theread efficiency loss is proportional to (W_(P) -W)/W_(P), where W_(P).Is the total width of the pole-tips and W is the width of thepinched-gap segment. The excess width of the pole-tips (W_(P) -W) shouldbe kept to a viable minimum. A practical range for the excess width is0.03P_(T) ≦(W_(P) -W)≦2.0P_(T),where P_(T) is the thickness of the toppole-tip.

It is preferable to use the pinched-gap TFH device in combination with aseparate read element, such as a magnetoresistive (MR) element, or aseparate inductive TFH element optimized for the read operation. Acombination with an MR read element is preferable, especially for highdensity small form disk drives. A particular combination is a merged MRread element, where the bottom pole-tip of the pinched-gap write elementis merged (or shared) with the top magnetic shield of the MR readelement. However, the fabrication of the additional MR element is highlycomplex and very costly. A simpler and more economic solution is tofabricate a separate inductive TFH element with conventional pole-tips,optimized for the read operation. A single head, incorporating thepinched-gap TFH device of this invention, can be used to perform boththe write and the read functions. However, due to the reduced readefficiency of the pinched-gap device, it is preferable to use separateheads (or elements), each of which is optimized to perform a singlefunction.

The separate write and read elements can be situated or placed one ontop of the other or in tandem with respect to the recorded track,side-by-side on the same rail (or air bearing surface), or on separaterails of the same slider. FIG. 11 illustrates the placement of apinched-gap write element 27 on top of an MR read element 25, as seen inperspective from the air bearing surface (ABS). The substrate 10 isshaped into a slider 1, including rails 2 and 3, and alumina 11 servesas undercoat, gap material, and overcoat. Placing an inductive writeelement in tandem with an MR read element is a common practice. Magneticshield layers (not shown) are required between the elements to preventmagnetic and electrical interferences. However, the fabrication processis highly complex, with low throughput and yield, and with highmanufacturing cost. Placing inductive write and read elements in tandemwith each other (as in U.S. Pat. No. 4,219,853 by Albert et al.) suffersserious drawbacks. The two elements interfere magnetically andelectrically with each other, and the fabrication process is very long,complex, and costly. The two elements can preferably be placedside-by-side on the same rail (or ABS), or on separate rails of theslider. FIGS. 12 and 13 illustrate the placement side-by-side on thesame rail, and on separate rails, respectively, of a pinched-gap writeelement and an MR read element. A pinched-gap TFH write element can beplaced similarly relative to an inductive TFH read element. Suchconfigurations require a fixed-translation scheme for the TFH slider toposition the read element over the written track for a read-back orverification operations after a write operation. The fixed-translationis in a plane parallel to the medium surface and in a directionessentially normal to the track's length. The fixed-translation takesonly a very short time.

Alternatively, multiple TFH sliders per medium surface, attached toseparate actuators, are positioned in such a way that the read elementof one slider follows behind the written track of another slider's writeelement. Such a track-following scheme minimizes the time lapse betweena write operation and read-back or verification operations and is fasterthan any of the current state-of-the-art configurations. Also, thetrack-following scheme completely eliminates all interference betweenthe write and read elements.

Placement of the write and read elements either side-by-side on the samerail, or on separate rails, has the advantages of much simpler, faster,and less costly fabrication. In addition, electrical and magneticinterference are substantially eliminated in such configurations. It isalso possible to construct multiple pairs of write and read elements onseparate rails (see FIG. 12). Each pair comprises a pinched-gap writeelement and a read element placed side-by-side on the same rail of a TFHslider. Such a configuration can significantly improve device yield, byredundancy, or multiply the data transfer rate of a disk-drive byutilizing simultaneous (or parallel) multiple channels.

The shorted sides or edges of the pole-tips in the pinched-gap devicevirtually eliminate the edge-closure domains in the pole-tips, therebyimproving significantly the head's SNR. Edge-closure domains aredescribed, for example, by D. A. Herman in paper No. 299, "LaminatedSoft Magnetic Materials", The Electrochemical Society Conference,Hollywood, Fla. October 1989. The deleterious edge-closure domains takelonger time to move than to rotate the 180° (easy axis) domains. Theythus cause noise due to their delayed response. The SNR degradationrelated to the edge-closure domains is proportional to their fraction ofthe entire domains in the pole-tips. With the conventional prior-artpole-tips, the SNR degradation increases as the pole-tip's width shrinksand approaches twice the size of the edge-closure domains. With thepinched pole-tips of this invention, most of the edge-closure domainsare eliminated by the shorted sides and side-edges.

In a preferred embodiment of the invention, one pole-tip (usually thebottom one) of the pinched-gap device is much wider than the other. Sucha configuration can be found in a merged MR (MMR) device, or it may beadvantageous to use in a regular inductive head. The wider pole-tipenables simple and straightforward fabrication, without the need forpole-trimming or additional masks. FIGS. 14a-14c show an air bearingsurface (ABS) view demonstrating a simple fabrication technique, usinggap-vias, to obtain the pinched-gap structure over a wider bottompole-tip. In order to simplify the drawing, features below the bottompole-tip such as the substrate and undercoat (and bottom shield,read-gap, and MR element and contacts, in the case of MMR device) wereexcluded.

FIG. 14a shows the situation after gap-vias 16a and 16b were patternedand etched, followed by removal of the gap-etch mask. The gap-vias canbe defined and etched in a similar process to the one described in FIG.6 above. As described there, the pole-tip vias can be done at the sametime and with a (modified) mask used to open the back gap-via (notshown). The latter is required to connect the backs of the bottom andtop pole yokes. The distance W between the gap-vias 16a and 16b definesthe width of the pinched-gap section 16, to be later formed insuccessive steps.

The next steps are shown in FIG. 14b. A seed-layer 30, such as Ni--Fe,is deposited (such as by sputtering) over the wafer, and a plating mask32, such as a photoresist mask, is formed over seed-layer 30. However,if the top pole is to be deposited by a vacuum technique (such assputtering or evaporation), then seed-layer 30 can be omitted. Theopening W_(P) in mask 32 determines the final width of the top pole-tip(including the side magnetic shunts). For proper functionality, theinternal edges of mask 32 opening, at the pole-tip region, should bealigned within the gap-vias, as shown in FIG. 14b. Following theformation of plating mask 32, top magnetic pole 18 is plated throughmask 32. Alternatively, top magnetic pole 18 can be deposited by avacuum technique (such as sputtering or evaporation). In this case mask32 is lifted-off following the top magnetic pole deposition.

In another alternative (not shown), top magnetic pole 18 is vacuumdeposited or plated, without a mask, onto the configuration seen in FIG.14a. Following the deposition of the top magnetic pole 18, an etch maskis formed over it. The alignment of the etch mask should protect the toppole-tip and shunts, as well as the back yoke. The outside edges of theetch mask, separated by a distance W_(P) in the pole-tip region, shouldbe located over gap-vias 16a and 16b. Following the formation of theetch mask, the wafer is subject to a dry etch (such as ion-milling orRIE) or to a wet chemical etch. For better precision, the dry etchtechnique is preferred. Adequate etch masks may comprise a metal orseveral metal layers and/or a photoresist layer.

FIG. 14c shows the completed pinched-gap section 16, following thedeposition of the top magnetic pole 18 and the removal of mask 32 andseed-layer 30. It also shows the configuration following the removal ofthe etch mask (not shown), in the case of deposition of the top polewith no mask, and its etching through an etch mask). As seen in FIG.14c, side shunts 19a and 19b are located within gap-vias 16a and 16b,respectively. The width W_(P) of the top pole-tip including the shunts,should be smaller than the distance L between the outside edges of thegap vias, but larger than the distance W between the gap-vias (also thewidth of pinched-gap section 16): W<W_(P) <L. The techniques describedin FIGS. 14a-14c are suitable to produce shunt widths in the range of0.3-3.0 μm, and more preferably, in the range of 0.5-2.0 μm.

FIGS. 15a-15d describe another convenient method for constructingpinched-gap structure with a wider bottom pole-tip. The method isparticularly suitable for obtaining relatively narrow, self-aligned sidemagnetic shunts. The technique can provide a shunt width in the range of0.05-1.0 μm, and more preferably, in the range of 0.1-0.5 μm. FIG. 15ashows (from ABS view) the situation after usual plating of the top pole(including pole-tip 18) through a frame (or "moat") plating mask,followed by removal of the plating mask. The latter was located in frameareas designated as 34a and 34b. Prior to forming the plating mask, aseed-layer 30, such as Ni--Fe, was deposited over gap layer 16. Duringthe plating of top magnetic pole 18, other areas, 18a and 18b, outsideframe (or moat) areas 34a and 34b, were also plated with the samemagnetic material. These areas are referred to as the field platedareas. The plated magnetic pole(s) and the field may comprise a softferromagnetic alloy, such as Ni--Fe. Plated top pole-tip 18 and thefield areas 18a and 18b can be used as a self-aligned mask for etchingthe gap 16 in frame areas 34a and 34b. However, prior to etching the gapin these areas, seed-layer 30 must be removed in these areas. This canbe accomplished by either a short dry or wet etch. In the case of dryetch, it may comprise a sputter etch, ion-milling, or a RIE technique.In the case of a wet etch, it may comprise a short dip or spray in asuitable chemical etch. A dry etch is preferred, since it offers bettercontrol and consistency. Next, the gap in frame areas 34a and 34b isetched using pole-tip 18 and field areas 18a and 18b as a self-alignedmask. Again, the gap can be etched either by a dry technique(ion-milling, RIE, or sputter-etch) or by a wet technique. In the firstcase, RIE is the preferred method, since it leaves relatively straightwalls and provides minimal attack on the plated top pole-tip 18, fieldareas 18a and 18b, and bottom pole-tip 14 (once exposed to the etching).However, wet etching might be a better method since it also highlyselective (does not attack the plated poles and field areas) and is veryfast and economic. A convenient wet etchant comprises one (1) volume ofconcentrated HF (48 wt %) diluted in nine (9) volumes of pure water (10%v/v). Etching can be carried out by immersion or by spray. However,being isotropic, wet etching of the gap produces some undercutting ofgap layer 16 (under top pole-tip 18).

FIG. 15b shows the stage after gap 16 was etched in frame areas 34a and34b and a new soft ferromagnetic seed-layer 19 was deposited over thestructure. Ferromagnetic seed-layer 19 can be deposited by a vacuumtechnique such as sputtering or evaporation. Following the deposition offerromagnetic seed-layer 19, the width of magnetic side shunts 19a and19b can be readily fortified (or increased) by plating moreferromagnetic material(s) over the seed-layer. Although it may be moreconvenient to form ferromagnetic seed-layer 19 and the fortifying platedlayer of the same material used for the top pole-tip, otherferromagnetic materials may offer better matching of the shuntreluctance to the pinched-gap reluctance. Thus, ferromagnetic materialswith lower permeability than that of the pole-tips will increase theshunt reluctance. Either the seed-layer alone and/or the fortifyingplated ferromagnetic layer may be different than the magneticmaterial(s) used in the pole-tips. A convenient ferromagnetic materialfor the pole-tips and for the shunts comprises permalloy Ni--Fe alloy.Different ferromagnetic materials may be used to construct top andbottom pole-tips 14 and 18.

FIG. 15c shows the stage after ion-milling (the preferred technique dueto its highly directional action, thereby leaving the side shunts 19aand 19b essentially untouched). The ion-milling is used to removeferromagnetic seed-layer and (if used) fortifying plated layer 19 fromframe areas 34a and 34b. Side magnetic shunts are now defined with ashunt width (W_(P) -W)/2. A field-etch mask (not shown) is formed overtop pole-tip 18 and side shunts 19a and 19b,as well as over frame areas34a and 34b. The wafer is then subjected to a field-etch that removesplated field areas 18a and 18b and their side layers 19. The field-etchis conveniently carried out by immersion or by spray in an appropriatechemical, such as acidic ammonium persulfate, or by a dry technique,such as ion-milling or RIE. The order of operations described above canbe reversed, i.e, the field-etch operation can precede the operation ofion-milling removal of the seed-layer 19 and (if used) the fortifyingplated layer from frame areas 34a and 34b.

The field-etch operation is preferably performed by a wet etch, in whichcase a protective thin layer (not shown) such as Au or Cu may berequired. Such a protective layer can be deposited by plating(preferably) or by vacuum deposition, over the structure shown in FIG.15b, or over the structure shown in FIG. 15c. The purpose of theprotective layer is to protect bottom pole-tip 14 against attack (i.e,undercutting) in frame areas 34a and 34b. Following deposition of theprotective layer, the field-etch mask is formed over the top pole-tip,side shunts, and frame areas 34a and 34b. Prior to the field-etchoperation, the protective layer in the exposed areas (over field areas18a and 18b) is removed by a wet selective etching or by sputter etchingor by ion-milling. The wafer is then subjected to the field-etch. Usingthis scheme, it is preferable to reverse the order of operations, wherethe field-etch operation precedes the step of ion-milling of thematerial of the seed-layer 19 in frame areas 34a and 34b.

FIG. 15d shows the final stage with the fully constructed pinched-gapstructure and a wide bottom pole-tip.

EXAMPLES Example 1

A pinched-gap TFH device was fabricated using a top pole-tip that iswider than the bottom pole-tip and by wraparound on both side-edges, asshown in FIG. 7. No further attempt was made to expose the side-edges ofthe bottom pole-tip. Virtual contacts along the bottom pole-tip'sside-edges were established due to the poor step coverage of the gaplayer there. The device performance was compared with a conventional TFHdevice having the same bottom pole-tip width and narrower top pole-tip.The heads were used for both the write and the read functions.Significant reduction of the track-edge fringing noise was observed forthe pinched-gap device. The track definition was substantially improved,and its width slightly decreased. The read-back signal of thepinched-gap device was somewhat decreased, but the device could still beused as a reader.

Example 2

Gap-vias were defined by photolithography, as in FIGS. 6 and 9. Metalliclayer 20 consisted of 300 Å thick sputter-deposited permalloy (Ni--Fe).Gap layer 16 consisted of 0.8 μm thick sputter-deposited Al₂ O₃. The viapattern was transferred to the permalloy layer 20 by etching thepermalloy, through photoresist mask 22, with an (1:1:8) etchantcomprising:

    ______________________________________                                        Nitric Acid (conc.)                                                                             HNO.sub.3  1 volume                                         Phosphoric Acid (conc.)                                                                         H.sub.3 PO.sub.4                                                                         1 volume                                         Water             H.sub.2 O  8 volumes                                        ______________________________________                                    

Etching was performed at room temperature by dipping the wafers in theetchant with moderate agitation. Visual inspection after 2 minutes ofetching, indicated completion of the permalloy etching in the via areas.Probe measurement in these areas exhibited extremely high electricalresistance, further indicating the completion of etching the permalloylayer 20. To check the latitude of the process, etching times as long as10 minutes were tried, with excellent fidelity and no visibleundercutting or any other problem. This constitutes a safe overetch timeof at least 400% with no visible undercutting. The etch rate ofpermalloy layer 20 through the mask was at least 150 Å/min. Next, thewafers were rinsed in pure water, and the exposed gap areas were etchedthrough the etch mask (combined of the photoresist and the permalloylayers). The etchant comprised:

    ______________________________________                                        Hydrofluoric Acid (48%)                                                                          HF        1 volume                                         Water              H.sub.2 O 9 volumes                                        ______________________________________                                    

Etching was performed by spraying the etchant at room temperature. Bothvisual inspection and electrical probe measurements (resistance of about1-3 Ohms) indicated completion of the gap-vias etching after 3 minutes.To check the latitude of this process, etching times as long as 9minutes were tried with high fidelity and no visible undercutting. Thisconstitutes a safe overetch time of at least 200%. The etch rate of thegap-vias under these conditions was about 2,700 Å/min. Following thecompletion of etching the gap-vias, the wafers were rinsed in pure waterand photoresist layer 22 was stripped by dipping in a commercialstripper. Next, permalloy layer 20 was removed by either a briefsputter-etching or by dipping in the 1:1:8 etchant (comprising nitricacid, phosphoric acid, and water) at room temperature. In the lattercase it only took about 30 seconds to remove the unmasked permalloylayer. This corresponds to etch rate of about 600 Å/min for the unmaskedpermalloy layer 20. Occasionally, this etchant caused pin-holes andsmall craters in relatively large exposed areas of the permalloy bottompole 14. Such larger exposed areas are used for other purposes, such aslapping guides or test features. To avoid this problem, very briefsputter-etching or ion-milling is preferred for the removal of permalloylayer 20. However, these techniques slightly attack the gap layer, aftermetallic layer 20 is removed. Using thinner permalloy layer, such as 100Å thick, minimizes both wet and dry etching time and the associateddeleterious effects. The preferred process calls for 100 Å thickpermalloy layer 20, and its removal by brief sputter-etching of lessthan 30 seconds.

Although examples and detailed embodiments were described for apinched-gap thin film head (TFH), other devices, such as ferrite metalin gap (MIG) heads, horizontal (such as planar silicon) heads, tapeheads, and perpendicular recording heads may also comprise thepinched-gap structure. The pinched-gap structure in all these devices isfacilitated by confining (or enclosing) a pinched-gap section betweentwo side magnetic shunts.

While the invention has been particularly described with reference topreferred embodiments, it will be understood by those skilled in the artthat various changes in form and detail may be made therein withoutdeparting from the spirit, scope, and teaching of the invention.Accordingly, examples herein disclosed are to be considered merely asillustrative and the invention to be limited only as specified in theclaims.

I claim:
 1. A thin film head (TFH) comprising a pinched-gap inductivemagnetic transducer device, said device comprising:a substrate; a bottommagnetic pole deposited over said substrate, said bottom magnetic polecomprising a back-portion and a bottom pole-tip; a non-magnetic gaplayer deposited over said bottom magnetic pole; a top magnetic poledeposited over said gap layer, said top magnetic pole comprising aback-portion and a top pole-tip, said back-portion of said top magneticpole being connected to said back-portion of said bottom magnetic pole;both of said pole-tips terminating at a surface which is to be locatedadjacent a magnetic recording medium when said device is writing data;said top pole-tip and said bottom pole-tip being in substantial contactwith each other in two areas so as to define a pinched-gap segment ofsaid gap layer in a central region between said two areas of substantialcontact, a width of one of said pole-tips being greater than a width ofthe other of said pole-tips; whereby a magnetic reluctance between saidpole-tips in said areas of substantial contact is substantially lowerthan a magnetic reluctance between said pole-tips across saidpinched-gap segment, thereby substantially preventing magnetic fluxlines from spreading laterally outward from said two areas ofsubstantial contact and thereby preventing the creation of significanttrack edge noise in a data track written by said device.
 2. The TFH ofclaim 1 further comprising a magnetoresistive (MR) device, said widerpole-tip comprising at least a portion of a magnetic shield for a readelement in said MR device.
 3. The TFH of claim 2 wherein said inductivemagnetic transducer device and said MR device are positioned in tandem,with one of said devices being on top of the other of said devices. 4.The TFH of claim 1 further comprising a magnetoresistive (MR) device, amagnetic shield for a read element in said MR device comprising at leasta portion of said wider pole-tip.
 5. The TFH of claim 1 wherein amagnetic shunt is positioned in each of said two areas of substantialcontact.
 6. The TFH of claim 5 wherein said magnetic shunt comprises amaterial that is different from a material comprised in at least one ofsaid pole-tips.
 7. The TFH of claim 6 wherein said top pole-tipcomprises a material different from a material comprised in said bottompole-tip.
 8. The TFH of claim 5 wherein a depth of the magnetic shuntextends from a front end of said pole-tips to zero-throat-height.
 9. TheTFH of claim 5 wherein a depth of the magnetic shunt extends to alocation between zero-throat-height and a front end of said pole-tips.10. The TFH of claim 1 wherein said two areas of substantial contactfunction to prevent significant side-edge fringing when said TFH is in anormal write operation.
 11. The TFH of claim 10 wherein said pole-tipscontact each other in said two areas.
 12. The TFH of claim 1 wherein aseparation between the pole-tips in said two areas of substantialcontact is less than 5% of a thickness of the gap layer between thepole-tips across said pinched-gap segment in said central region.
 13. Apinched-gap magnetic recording head comprising:first and second magneticpole-tips, said first and second magnetic pole-tips terminating at asurface which is to be located adjacent a magnetic recording medium whensaid head is writing data; a nonmagnetic transducing gap separating saidpole-tips, said transducing gap being confined by a pair of sidemagnetic shunts, said transducing gap being located in a central regionbetween said side magnetic shunts, wherein each of said side magneticshunts is in substantial contact with both of said pole-tips throughouta region beginning at said surface and extending along said pole-tipsaway from said surface, and wherein a magnetic reluctance between saidpole-tips through said magnetic shunts is substantially lower than amagnetic reluctance between said pole-tips across said transducing gap,thereby substantially preventing magnetic flux lines from spreadinglaterally outward from said pole-tips and thereby preventing thecreation of significant track edge noise in a data track written by saidmagnetic recording head.
 14. The pinched-gap recording head of claim 13wherein each of said side magnetic shunts is in substantial contact withthe side-edges of at least one of said pole-tips.
 15. The pinched-gaprecording head of claim 1 or claim 13 wherein said head is selected froma group consisting of thin film heads, metal in gap heads, horizontalheads, planar silicon heads, tape heads, and perpendicular recordingheads.
 16. A pinched-gap magnetic recording head comprising:first andsecond magnetic pole-tips, said first and second magnetic pole-tipsterminating at a surface which is to be located adjacent a magneticrecording medium when said head is writing data; a nonmagnetic gap layerseparating said pole-tips; said pole-tips being in substantial contactwith each other in two areas so as to define a pinched-gap segment ofsaid gap layer in a central region between said areas of substantialcontact, said areas of substantial contact beginning at said surface andextending a distance along said pole-tips away from said surface, athickness of said gap layer being such that a transducing gap is formedbetween said pole-tips in said central region, there being no thirdmagnetic pole-tip located between said first and second magneticpole-tips within said central region, a width of said first magneticpole-tip being greater than a width of said second magnetic pole-tip;whereby a magnetic reluctance between said pole-tips in said areas ofsubstantial contact is substantially lower than a magnetic reluctancebetween said pole-tips across said transducing gap, therebysubstantially preventing magnetic flux lines from spreading laterallyoutward from said pole-tips and thereby preventing the creation ofsignificant track edge noise in a data track written by said device. 17.The pinched-gap magnetic recording head of claim 16 wherein a separationbetween the first and second magnetic pole-tips in each of said twoareas of substantial contact is less than 5% of a thickness of said gaplayer between said first and second magnetic pole-tips in said centralregion.
 18. A thin film head (TFH) comprising a pinched-gap inductivemagnetic transducer device, said device comprisinga substrate; a bottommagnetic pole formed over said substrate, said bottom magnetic polecomprising a back-portion and a bottom pole-tip; a non-magnetic gaplayer formed over said bottom magnetic pole; a top magnetic pole formedover said gap layer, said top magnetic pole comprising a back-portionand a top pole-tip, said back-portion of said top magnetic pole beingconnected to said back-portion of said bottom magnetic pole, both ofsaid pole-tips terminating at a surface which is to be located adjacenta magnetic recording medium when said device is writing data; said toppole-tip and said bottom pole-tip being in substantial contact with eachother in two areas so as to define a pinched-gap segment of said gaplayer in a central region between said two areas of substantial contact,said areas of substantial contact beginning at said surface andextending a distance along said pole-tips away from said surface;whereby a magnetic reluctance between said pole-tips in said areas ofsubstantial contact is substantially lower than a magnetic reluctancebetween said pole-tips across said pinched-gap segment, therebysubstantially preventing magnetic flux lines from spreading laterallyoutward from said pole-tips and thereby preventing the creation ofsignificant track edge noise in a data track written by said device. 19.The head of claim 14, 16 or 18 further comprising a magnetoresistive(MR) device.
 20. The head of claim 19 wherein said pole-tips arecomprised in an inductive magnetic transducer device, said inductivemagnetic transducer device and said MR device being positioned intandem, one of said devices being on top of the other of said devices.21. The head of claim 20 wherein said MR device includes top and bottommagnetic shields, said top magnetic shield comprising at least a portionof one of said pole-tips.